The goal of this project is to evaluate the toxicity C9-alkylbenzenes, including 1,2,4-trimethylbenzene and a representative ethyltoluene isomer, following exposure via inhalation. Three-month studies of both compounds are in the prestart chemistry/inhalation phase. Humans are likely to be similarly exposed to these compounds via inhalation. These subchronic studies will provide valuable data on general toxicity as well as reproductive and neurotoxicity and will aid in the design of chronic toxicity/carcinogenicity studies. Keywords: toxicity, inhalation, vanadium, trimethylbenzene, ethyltoluene.